Is the prayer valid in the case of doubt between the second and third rak'ahs, by building upon it as the second, with a strong feeling to that effect?

If you are afflicted with doubt and question the number of rak'ahs, then consider it the third rak'ah and do not pay attention to the possibility of it being the second; for the person afflicted with obsessive doubts relies on the first thought that occurs to them. Whoever doubts the number of rak'ahs should base their decision on certainty, while the person with obsessive doubts builds upon the first thought. If they are afflicted with obsessive doubts, they should build upon their first thoughts. So, if they are certain that they have completed it, they should act accordingly. If they are certain that they have not completed it, they should perform what they doubted. It should be noted that doubt after the prayer is not to be considered.